We calculate accretion mass of interstellar objects ( ISOs ) like ‘ Oumuamua onto low-mass population III stars ( Pop .
III survivors ) , and estimate surface pollution of Pop .
III survivors .
An ISO number density estimated from the discovery of ‘ Oumuamua is so high ( \sim 0.2 au ^ { -3 } ) that Pop .
III survivors have chances at colliding with ISOs \gtrsim 10 ^ { 5 } times per 1 Gyr .
‘ Oumuamua itself would be sublimated near Pop .
III survivors , since it has small size , \sim 100 m. However , ISOs with size \gtrsim 3 km would reach the Pop .
III survivor surfaces .
Supposing an ISO cumulative number density with size larger than D is n \propto D ^ { - \alpha } , Pop .
III survivors can accrete ISO mass \gtrsim 10 ^ { -16 } M _ { \odot } , or ISO iron mass \gtrsim 10 ^ { -17 } M _ { \odot } , if \alpha < 4 .
This iron mass is larger than the accretion mass of interstellar medium ( ISM ) by several orders of magnitude .
Taking into account material mixing in a convection zone of Pop .
III survivors , we obtain their surface pollution is typically [ Fe/H ] \lesssim - 8 in most cases , however the surface pollution of Pop .
III survivors with 0.8 M _ { \odot } can be [ Fe/H ] \gtrsim - 6 because of the very shallow convective layer .
If we apply to Pop.III survivors located at the Galactocentric distance of 8 kpc , the dependence of the metal pollustion is as follows .
If \alpha > 4 , Pop .
III survivors have no chance at colliding with ISOs with D \gtrsim 3 km , and keep metal-free .
If 3 < \alpha < 4 , Pop .
III survivors would be most polluted by ISOs up to [ Fe/H ] \sim - 7 .
If \alpha < 3 up to D \sim 10 km , Pop .
III survivors could hide in metal-poor stars so far discovered .
Pop .
III survivors would be more polluted with decreasing the Galactocentric distance .
Although the metal pollution depends on \alpha and the Galactocentric distance , we first show the importance of ISOs for the metal pollution of Pop .
III survivors .